Liquid-discharging head, liquid-discharging device, and method of producing the liquid-discharging head

ABSTRACT

The present invention is applicable to, for example, a thermal printing head to form shallow grooves M by removing the insulating films  21, 24, 30 , and  33  along at least the rows of the energy transducers.

BACKGROUND OF INVENTION

The present invention relates to liquid-ejecting heads, liquid-ejectingapparatuses, and methods for manufacturing liquid-ejecting heads, andrelates to, for example, a thermal printing head. According to thepresent invention, insulating films on wafers are removed to formshallow grooves along at least rows of energy transducers. In thismanner, the grooves can prevent various types of damage due to crackingand chipping even during high-speed dicing.

In printers provided with printing heads ejecting ink droplets, energytransducers convert electric energy into energy for ejecting ink.Heating devices are used as the energy transducers for thermal printingheads.

In thermal printing heads, heating devices heat ink contained in inkchambers to generate bubbles, and the ink droplets are ejected fromnozzles by the pressure of bubbling.

In such a printing head, heating devices and a driving circuit areintegrated densely on a semiconductor substrate, resulting inhigh-resolution printing. Moreover, the heads are efficiently producedthrough semiconductor manufacturing processes: Heating devices anddriving circuits for a plurality of chips are integrated on asemiconductor substrate, or wafer; the substrate is cut into chips; andink chambers and nozzles are provided on the chips.

FIG. 1 is a plan view of a semiconductor substrate manufactured by aknown process. In the process, a 6-inch silicon wafer 1, for example, issequentially processed to form, at a predetermined pitch, rectangularregions 2, each of which includes heating devices and a driving circuitfor one chip. In FIG. 1, the size of the regions 2 is illustrated largerthan their actual size relative to the silicon wafer 1.

FIG. 2 shows cutting regions 3 formed between the regions 2 duringprocessing of the silicon wafer 1 in a manufacturing process of theprinting heads. As shown in a cross-sectional view of FIG. 3, aprotective film 4 for preventing penetration of ink, and an insulatingfilm 5 under the protective film 4 are removed from the silicon wafer 1to form cutting region 3 wider than a blade used for dicing. In theexample shown in FIG. 3, the cutting region 3 has a width of 140 μm fora blade width of 50 μm.

In the process, the silicon wafer 1 is held on a stage of a dicingmachine. The stage or the blade rotating at high speed is driven suchthat the blade cuts the silicon wafer 1 substantially at the center ofthe cutting regions 3 into chips. In this step of fabricating printingheads, a stream of deionized water is provided to the areas to be cut inorder to cool the blade and wash away cutting debris.

In this dicing step, an impact due to increasing the cutting speedcauses cracking and chipping at the chip edges. FIG. 4 is a plan view ofan edge of the chip in FIG. 3. The chip is formed by cutting the siliconwafer 1 with a blade 50 mm in diameter rotating at a speed of 30,000 rpmand fed at a speed of 30 mm/sec, and has chipped portions ofapproximately 17 μm. The relative speed between the blade- and thesilicon wafer 1 under these conditions is given by 50[mm]×3.14×60×30,000/1,000,000=282 km/h. The collision of the blade withthe silicon wafer at high speed is a possible cause for cracking andchipping.

In a printing head, ink contained in ink chambers is heated by theheating devices on the chip, and droplets thereof are ejected as aresult. When cracking or chipping occurs in the chip, the ink canpenetrate into the chip and may cause instability of semiconductorperformance. When ink is introduced to the ink chambers from a side faceof the chip, the fluid resistance in the ink passage connected to theink chambers may change due to cracking or chipping, resulting in slightchanges in print quality. Furthermore, when the chipping fragmentsremain on the chip surface, these fragments can damage the chip surfaceduring forming of the ink chambers. In the event that the damage fromthe chipping fragments reaches inside the chip, ink will penetrate intothe chip, and a wiring pattern or the like may be damaged in the case ofsevere damage.

To prevent cracking and chipping of the chip, the cutting speed in theprocess of manufacturing printing heads should be slower than that in aprocess of manufacturing standard integrated circuits.

A method for dicing standard integrated circuits is disclosed in, forexample, Japanese Unexamined Patent Application Publication No.6-275713, in which grooves deeper than the depth of devices, such astransistors, are formed on both sides of the cutting regions in order toprevent the propagation of cracks during cutting.

In a manufacturing process of printing heads in which a 6-inch siliconwafer is cut along 60 longitudinal lines and 12 transverse lines to formchips at a cutting speed of 5 mm/sec, the time required for cutting is60×12×(150/5)/3,600=6 hours. Thus, the known dicing step for cuttingchips at low speed to avoid cracking and chipping disadvantageouslytakes time.

When the method disclosed in Japanese Unexamined Patent ApplicationPublication No. 6-275713 is applied as a solution for this problem, itrequires an additional etching step to form grooves deeper than thedevices. Besides, since it is not possible to avoid the chippingfragments, damage to the chip surfaces from the fragments is inevitable.

SUMMARY OF THE INVENTION

In view of the above-mentioned problems, the present invention providesa liquid-ejecting head, a liquid-ejecting apparatus, and a method formanufacturing the liquid-ejecting head in which various types of damagedue to cracking and chipping can be prevented even during high-speeddicing.

To solve these problems, the present invention is applied to aliquid-ejecting head ejecting droplets by driving energy transducers inwhich at least one groove is formed, parallel to at least the side facealong which the energy transducers are provided, by removing insulatingfilms.

In accordance with the structure of the present invention, the presentinvention can be applied to liquid-ejecting heads ejecting droplets bydriving the energy transducers, for example, liquid-ejecting heads whicheject ink droplets, dye droplets, droplets for forming protectivelayers, or the like; liquid-ejecting heads for microdispensers,measuring units, or testing units which eject droplets of reagents orthe like; and liquid-ejecting heads for pattern-drawing units whicheject droplets of agents that protect target components during etching.In accordance with the structure of the present invention, since atleast one groove is formed, parallel to at least the side face alongwhich the energy transducers are provided, by removing insulating films,the grooves can be formed simultaneously in a step of patterning theinsulating films. Thus, the grooves are efficiently formed withoutincreasing the number of processing steps. Such grooves prevent thepropagation of cracking and chipping to the chips, reduce the size ofchipping fragments, prevent penetration of liquid into the chips throughthe cracked or chipped portions, reduce the change in fluid resistancein the ink passage, and reduce the damage due to chipping fragments. Asmentioned above, various types of damage due to cracking and chippingcan be prevented by the grooves even during high-speed dicing.

The present invention is also applied to a liquid-ejecting apparatusejecting droplets by driving energy transducers on a liquid-ejectinghead. The head chip includes at least one groove that is formed,parallel to at least the side face along which the energy transducersare provided, by removing insulating films.

In accordance with the structure of the present invention, the presentinvention can provide a liquid-ejecting apparatus in which various typesof damage due to cracking and chipping can be prevented even duringhigh-speed dicing.

The present invention is also applied to a method for manufacturingliquid-ejecting heads ejecting droplets by driving energy transducers.Before a cutting step, the method includes a step of removing insulatingfilms to form grooves parallel to at least the side face along which theenergy transducers are provided.

In accordance with the structure of the present invention, the presentinvention can provide a method for manufacturing the liquid-ejectingheads in which various types of damage due to cracking and chipping canbe prevented even during high-speed dicing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing the layout of head chips on a siliconwafer.

FIG. 2 is a plan view illustrating cutting of the head chips.

FIG. 3 is a cross-sectional view illustrating cutting regions.

FIG. 4 is a plan view illustrating chipping.

FIG. 5 is a perspective view of a printing head according to a firstembodiment of the present invention.

FIG. 6 is a cross-sectional view of a head chip applied to the printinghead in FIG. 5.

FIGS. 7(A) and 7(B) are a plan view and a cross-sectional view,respectively, illustrating the layout of the head chips shown in FIG. 6on the silicon wafer.

FIG. 8 is a cross-sectional view showing the cutting region of the headchips shown in FIG. 6 on the silicon wafer.

FIG. 9 is a cross-sectional view showing the cutting region of thesilicon wafer according to a second embodiment of the present invention.

FIG. 10 is a plan view illustrating the layout of the head chipsaccording to another embodiment of the present invention.

FIG. 11 is a plan view in which all the head chips are aligned in thesame direction.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be described inmore detail while referring to the accompanying drawings.

1. First Embodiment

1.1 Structure of First Embodiment

FIG. 5 is a perspective view of a printing head applied to a printeraccording to an embodiment of the present invention. The printeraccording to this embodiment ejects ink droplets onto paper or the likeby driving energy transducers, namely heating devices, provided on aprinting head 11, and prints images or the like. The printing head 11 isformed by sequentially laminating a dry film 13 and an orifice plate 14on a head chip 12.

The head chip 12 is formed by cutting a silicon wafer processed byIC-technology, and a plurality of heating devices 17 and a drivingcircuit for driving the heating devices 17 are integrated therein. Theheating devices 17 are disposed at a predetermined pitch on the headchip 12. The dry film 13 is composed of organic resin. After the dryfilm 13 is press-bonded to the head chip 12, the dry film is partlyremoved to form ink chambers 15 and an ink passage 16, and then iscured. The orifice plate 14 has a predetermined shape, is provided withsmall ink-ejecting outlets, namely nozzles 19, above the respectiveheating devices 17 on the head chip 12, and is bonded to the dry film13. Thus, the printing head 11 includes the ink chambers 15 and the inkpassage 16 formed by the dry film 13 and the orifice plate 14 for thehead chip 12.

In this embodiment, the heating devices 17 are disposed on the head chip12 along a side face of the chip. In the printing head 11, the dry film13 has a comb shape so that the inlets of the ink chambers 15 are opento the side along which the heating devices 17 are disposed, and the inkpassage 16 is also formed along the side of the inlet openings. Thus, inthe printing head 11, ink is supplied from the side of the head chip 12and ink droplets are ejected by driving heating devices 17 on the headchip 12.

FIG. 6 is a cross-sectional view showing the structure of the head chip12. In the head chip 12, a silicon nitride (Si₃N₄) film is deposited andpatterned on a silicon substrate 20 obtained from a silicon wafer, and athermal oxidizing step is then performed with the silicon nitride(Si₃N₄) film functioning as a mask to form a thermal silicon oxide film21, namely a region for isolating devices (LOCOS: local oxidation ofsilicon). In the head chip 12, devices are isolated by the regions forisolating devices, and MOS (metal-oxide-semiconductor) transistors 22and 23 are formed.

In the head chip 12, a first insulating interlayer 24 composed ofsilicon oxide is formed, and contact holes 26 are then formed bypatterning the insulating interlayer 24. Subsequently, a film of amaterial for forming a wiring pattern is formed, and is etched to form afirst wiring pattern 27. In the head chip 12, the first wiring pattern27 formed in the above-mentioned step connects a transistor 22 withanother transistor 23 to form a logical circuit, and then the logicalcircuit and the switching transistor 23 which drives the heating device17 are connected.

In the head chip 12, a second insulating interlayer 29 composed ofsilicon oxide is formed, and a laminated resistor film is then patternedto form the heating device 17. Subsequently, an insulating film 30composed of silicon nitride is deposited and is etched to form a contacthole 31. Furthermore, a film of a material for forming a wiring patternis formed, and is patterned to form a second wiring pattern 32. In thehead chip 12, the second wiring pattern 32 forms lands for wiring apower supply, a ground, and various driving signals. These lands arethen connected to the driving circuit and the heating devices 17, sothat the heating devices 17 are connected to the transistor 23.

After an insulating film 33 composed of silicon nitride is formed, thehead chip 12 is heat-treated at a temperature of 400° C. for 60 minutesin an atmosphere of nitrogen gas containing 4% hydrogen or in anatmosphere of 100% nitrogen. Thus, the performance of the transistors 22and 23 of the head chip 12 is stabilized, and the connection between thefirst wiring pattern 27 and the second wiring pattern 32 is stabilizedto reduce the contact resistance. The heat-treatment is carried out byannealing to relieve the residual stress in the insulating interlayer 29or the like.

In the head chip 12, the insulating film 33 is partly removed to exposethe lands for the power supply, the ground, and various driving signals,and a tantalum anti-cavitation layer 34 is formed by sputtering. Then,after a dicing step to separate individual chips, the head chip 12 isintegrated in the printing head 11, as described in FIG. 5.

FIG. 7(A) is a plan view showing the layout of the head chips 12 on asilicon wafer 40 formed in the above-mentioned manner. The heatingdevices 17 on the head chip 12 face those on another adjacent head chip12 on the silicon wafer 40. The regions between the head chips 12 areallocated for cutting regions 39. As shown in FIG. 7(B), shallow narrowgrooves M away from the devices are formed along the cutting regions 39on the silicon wafer 40. According to this embodiment, the energytransducers, namely heating devices 17, are disposed along one of theedges of the head chips 12 and the shallow narrow grooves M are formedalong the edges of the head chips.

FIG. 8 shows the section A in FIG. 7(B) partly enlarged. When a blade isplaced at the center of the cutting regions 39 on the silicon wafer 40,the distance between grooves M is set to include margins of 8 μm on bothsides of the blade. Thus, according to this embodiment, the cuttingregions 39 are set narrower than the cutting regions 3 shown in FIG. 4described above as a known technique, and thus the head chips 12 areformed more densely on the silicon wafer 40.

On the silicon wafer 40, the region for isolating devices, namely thethermal silicon oxide film 21, the first insulating interlayer 24, thesecond insulating interlayer 29, and the insulating film 30 and 33 aresequentially formed also on the cutting regions 39 during processing ofthe head chip 12. In this manner, no level difference occurs between thehead chip 12 and the cutting regions 39 during the above-mentioned stepsof forming and patterning films, and the steps of patterning or the likeon the head chip 12 can be performed with high accuracy.

The grooves M are formed by partly removing the insulating interlayer 24and 29, and the insulating films 30 and 33. Before the thermal siliconoxide film 21 is formed, the portions of the silicon wafer 40 on whichthe grooves M are formed are masked by silicon nitride films so that thethermal silicon oxide film 21 is not provided on the portions forforming the grooves M. The insulating interlayer 24 on the portions forforming the grooves M is removed in the step of forming contact holes inthe insulating interlayer 24. The insulating interlayer 29 and theinsulating film 30 on the portions for forming the grooves M are alsoremoved in the steps of forming contact holes in the insulatinginterlayer 29 and the insulating film 30. The insulating film 33 on theportions for forming the grooves M is removed in the step of exposingthe lands for the power supply, the ground, and various driving signalsafter forming the insulating film 33.

In the process of forming the head chip, reticles are prepared forpatterning the insulating interlayer 24, the insulating interlayer 29,the insulating film 30, and the insulating film 33 so that the grooves Mare formed during these patterning steps. Therefore, the grooves M areformed without additional steps according to this embodiment. The widthof the grooves M is designed to be 2 μm at the deepest position.

1.2 Operation of First Embodiment

In the structure described above, the printing head 11 according to thisembodiment (shown in FIG. 5) is completed as follows: The transistors 22and 23, the heating devices 17 and the like are sequentially formed onthe silicon wafer 40; the wafer is cut with a dicing machine into theindividual head chips 12 (shown in FIG. 6); the dry film 13 ispress-bonded to the head chip 12 and processed; and the orifice plate 14is provided to form the ink chambers 15, the ink passage 16, and thelike.

In the printing head 11, ink is introduced to the ink chambers 15 formedas mentioned above through the ink passage 16 formed at the side of thehead chip 12. The droplets from ink contained in the ink chambers 15 areejected from the nozzles 19 by driving the heating devices 17 with thetransistors 22 and 23, and land on a target, for example, paper.

When chipping occurs at the side to which the ink is introduced, thefluid resistance in the ink passage connected to the ink chambers 15changes. This change appears in the meniscus and the volume of inkdroplets at the successive nozzles varies, resulting in low imagequality. When cracking occurs, the ink penetrates into the head chipfrom the side of the ink passage 16, and the performance of thetransistors 22 and 23 will become unstable. In contrast, when thechipping fragments due to cutting remain on the surface, the fragmentsare press-bonded to the head chip 12 with the dry film 13 and damage thesurface of the head chip 12. In the case of severe damage, the fragmentsmay be pushed into the head chip 12 and cause damage such as a breakingof wires.

In this manner (FIGS. 7 and 8), the head chips 12 are aligned on thesilicon wafer 40 so that the heating devices 17 on one chip face thoseon another chip, the cutting regions 39 are formed between the headchips 12, and the shallow grooves M are formed along the cutting regions39. Due to the grooves M, cracking and chipping on the head chip 12 arereduced when the cutting regions 39 are cut with a dicing machine forforming the head chips 12.

Since the grooves M are formed on either side of the cutting regions 39as mentioned above, the shearing stress is concentrated on the areabetween the grooves M, and cracking and chipping stop at the grooves M.Therefore, propagation of cracking and chipping to the head chip 12 canbe prevented.

In this embodiment, since such grooves M are formed along the rows ofthe heating devices 17, cracking and chipping can be prevented at theside of the head chip 12 which is in contact with ink, and therefore thepenetration of ink into the head chip 12 and changes in fluid resistancein ink passage can be prevented.

The size of the resulting products of chipping, namely chippingfragments, is small, so that the fragments can be washed away from thesurface of the head chip 12 with distilled water to reduce the damagecaused by the fragments.

In the manner according to this embodiment, various types of damage dueto cracking and chipping can be prevented even during high-speed dicing,and therefore, productivity is improved.

In this embodiment, the residual stress of the cutting segments in theinsulating interlayer 29, for example, is relieved by heat-treatmentbefore cutting. Accordingly, even when the tip of the blade of thedicing machine impacts the silicon wafer 40 at high speed, chipping andcracking on the silicon wafer 40 are significantly reduced compared tothe known process. In this manner, various types of damage due tocracking and chipping can be prevented even during high-speed dicing.

In the head chip 12, insulating films are partly removed to form groovesM in the steps of patterning the insulating interlayer 24, theinsulating interlayer 29, and the insulating film 30 to form the contactholes, and in the step of patterning the insulating film 33 to exposethe lands for the power supply or the like. Thus, the grooves areefficiently formed without increasing the number of processing steps,and various types of damage due to cracking can be prevented by thegrooves M.

Since heat-treatment is performed simultaneously during theheat-treatment of the transistors 22 and 23 for stabilizing theperformance, a further annealing step is not required.

When a wafer was cut under the conditions described with reference toFIG. 3, only microscopic chipping was observed on the edge of the cutsurface. When the chipped portion was magnified, it was found that thechipping propagation was blocked at the grooves M.

1.3 Effects of First Embodiment

According to the structure above, various types of damage due tocracking and chipping can be prevented on the head chip 12, even duringhigh-speed dicing, by removing the insulating films to form the shallowgrooves along the edges of the head chip 12 including the rows of theenergy transducers, namely heating devices 17.

Since the insulating films to be removed function as the insulatinginterlayers for wiring patterns, the grooves are also formed duringpatterning of the insulating interlayers.

Since the insulating films to be removed function as protective filmsbetween the energy transducers, namely heating devices, and ink, thegrooves are also formed during patterning of the protective films toexpose the lands.

By the heat-treatment step for relieving the residual stress in theinsulating films before cutting, cracking and chipping is furtherreduced, and therefore, various types of damage due to cracking andchipping can be further prevented.

2. Second Embodiment

FIG. 9 is a cross-sectional view showing the cutting region 39 betweenthe head chips 12 applied to a second embodiment of the presentinvention compared to FIG. 8. In the embodiment, the grooves M areformed by removing the insulating film 30 and 33. Since the embodimenthas the same structure as the first embodiment except for the steps toform the grooves M, a duplicated explanation will be omitted.

In the embodiment, the thermal oxide film 21 is not formed on theportions for forming the grooves M on the silicon wafer 40. Theinsulating interlayer 24 on the portions for forming the grooves M isremoved during forming of the contact holes in the insulating interlayer24. The insulating film 33 on the portions for forming the grooves M isalso removed during exposing of the lands. Accordingly, the grooves Mformed in this embodiment are shallower than those in the firstembodiment.

According to the structure of the second embodiment, forming the groovesby partly removing the insulating films achieves the same effects as thefirst embodiment.

3. Other Embodiments

The present invention is not limited to the above embodiments in whichcracking and chipping are reduced at all the side faces of a head chipby forming grooves on either side of the cutting regions. A groove M maybe formed only along each row of the heating devices 17 if necessary. Asshown in FIG. 10, for example, grooves M are formed only on the portionsalong the rows of the heating devices 17, and sufficient spaces areallocated for the cutting regions on which the grooves M are not formed.In this arrangement, cracking and chipping can be reduced by the groovesM at the side to which ink is supplied, and therefore penetration of inkand a change in fluid resistance in the ink passage can be prevented.

The present invention is not limited to the above embodiments in whichheating devices on a chip are aligned to face those on the adjacentchip. All the head chips may be aligned in the same direction, as shownin FIG. 11 compared to FIG. 7. In this case, a groove M may be formedonly at the cutting regions adjacent to the heating devices 17.

The present invention is not limited to the above embodiments in whichheat-treatment is performed after forming the uppermost layer, that is,the insulating film 33. Since the heat-treatment before dicing reducescracking or the like, the heat-treatment may be performed in any stepbefore dicing, if necessary. When cracking or the like is allowable, theheat-treatment can be omitted.

The present invention is not limited to the above embodiments in which alogical circuit includes MOS transistors. The present invention is alsoapplicable to logical circuits which include bipolar transistors.

The present invention is not limited to the above embodiments in which adriving circuit and energy transducers are integrated on a head chip.The present invention is also applicable to the head chip which includesthe energy transducers alone.

The present invention is not limited to the above embodiments in whichheating devices function as energy transducers. Various types of energytransducers can be used in another embodiment. Electrostatic actuatorsthat change the pressure in ink chambers by static electricity, forexample, may function as energy transducers.

The present invention is not limited to the above embodiments involvinga printing head which ejects ink droplets. The present invention is alsoapplicable to printing heads which eject dye droplets, droplets forforming protective layers, or the like, instead of ink droplets;microdispensers, measuring units, or testing units which eject dropletsof reagents or the like; pattern-drawing units which eject droplets ofagents that protect target components during etching; and the like.

According to the present invention described above, various types ofdamage due to cracking and chipping can be prevented by removing theinsulating films to form shallow grooves along at least the rows of theenergy transducers even during high-speed dicing.

INDUSTRIAL APPLICABILITY

The present invention relates to liquid-ejecting heads, liquid-ejectingapparatuses, and methods for manufacturing the liquid-ejecting heads,and relates to, for example, a thermal printing head.

1. A method for manufacturing a liquid-ejecting head for ejectingdroplets by driving energy transducers, comprising: a forming step offorming a row of a plurality of the energy transducers on asemiconductor substrate; a cutting step of cutting the semiconductorsubstrate along the row of the energy transducers to form a head chip;an assembling step of assembling the head chip into the liquid-ejectinghead; a removing step of removing an insulating film for forming agroove on the head chip parallel to at least a side face along which theenergy transducers are provided before the cutting step; and anannealing step for relieving residual stress in the insulating film. 2.The method for manufacturing the liquid-ejecting head according to claim1, wherein the insulating film is an insulating interlayer for a wiringpattern, and the removing step of the insulating film is a patterningstep of the insulating interlayer.
 3. The method for manufacturing theliquid-ejecting head according to claim 1, wherein the insulating filmis a protective film prepared between the energy transducers and theliquid, and the removing step of the insulating film is a patterningstep of the protective film.